For each translation file which includes the serialization type and the archive type shows one extended_type_info in tkmap for that serialization type. The serialization type is surely on one DLL only, because they're only defined there. No other project has access to those headers (not in usage-requirements for other projects).
What is "translation file" as opposed to a DLL?. Is the DLL loaded explicitly with "library load" or automatically as an "import library"?
Multiple registration records could occur from having code for the same type in multiple DLLS or in a DLL along with the main module.
I will try to provide a boost.build-v2 buildable example with the problem when I can in the near time.
Good luck with that. I couldn't figure out a way to make bjam do this. Robert Ramey